Is PU foam between the sealing tape and window normal or not?

  • Erstellt am 2018-03-04 22:30:54

AltbauSan18

2018-03-04 22:30:54
  • #1
Hi,
I have been planning and partly carrying out my old building renovation for a few months now. After a lot of back and forth about which windows are better and whether the roller shutter boxes should be replaced or not, we finally made a decision.

We thought the issue was finally settled.

Now the windows are installed, but I have my doubts about the way they were installed.

The window installer said during the sales talks that he installs according to RAL and that a sealing tape is prescribed for this. For that, the reveals would have to be finely plastered.

A company known to the window installer then did exactly that.

However, I was surprised that foam was still used between the sealing tape and the reveal. When I asked an employee why this was necessary, he said the gap between the window and the reveal was too large and otherwise it would not be airtight. Later, I was told it was done because of the cold weather (it was below freezing) since the tape did not expand.

I would like to hear or read your opinions on the following points.

1. If foam was used anyway, couldn't the sealing tape have been omitted altogether?
2. If yes, could I then have also saved myself the fine plastering? (After removing the windows and knocking off the old plaster, the reveals were relatively even anyway)
3. Is it still RAL compliant if only foam was sprayed between the window and the reveal?
By the way, only foam was used under the window anyway, because the other company allegedly built the lower window reveal a bit too high (where the previous bentonite window sill was)
4. Was it even permissible to use the sealing tape at those temperatures? The Würth instructions at least specify a processing temperature of at least 5°C. Although there was heating inside, with several open >1.5m2-sized holes, that did not help much.

Furthermore, I have additional doubts.

It was always obvious to me that the substrate should be cleaned before any building materials or seals are used.

I was already surprised that no one asked me for water or that I never heard a vacuum cleaner. Then I saw that the window installers had not even swept the lower window reveal with a broom and simply sprayed the foam there. This surface was covered with a cement or mortar dust layer at least 2-3 mm thick.
I would say the foam adheres to the dust but not to the underlying wall, or am I wrong?

Moreover, I noticed in some places that the sealing tape does not stick to the window. I assume this is either because the window frames were not cleaned in the dusty apartment before the tape was applied or because of the low temperatures or both.
What do you think?

Well, that's enough writing for now and I hope there are only a few typos... (It's really a struggle to write this on a smartphone)

Here are a few pictures:
 

lastdrop

2018-03-05 09:48:14
  • #2
I consider sealing tape and foam to be rubbish as a non-expert.
 

dertill

2018-03-05 10:32:14
  • #3
I recognize the following in the pictures: Between the window frame and the reveal, a "sealing tape," that is, a self-expanding wind-driven rainproof one-sided adhesive foam tape, was glued into the joint at the frame. This did not fill the joint between the window and the reveal around the frame, and therefore PU foam was additionally used for support. The tape now partly hangs in the window joint without any contact, partly there is still foam in between, and on the underside only foam was used for support? And that is all that was done for sealing the window?

One cannot install a worse mess on a component in one working step!

This "sealing tape" – which I would rather call a compression tape – serves for the OUTER! sealing of the joint between the window frame and the wall. It should always be fixed with the adhesive side on the frame, and the non-adhesive side should rest against the masonry. For brick facades or those with an internal rebate, i.e., where the frame is set inside against a projection in the masonry, this should be done from the inside against the brick, otherwise on the side, as far outside as possible. The tape is wind-driven rainproof and vapor-permeable and according to the manufacturer also airtight. But this only applies if it is firmly adhered on both sides. In your case, it just hangs loosely there and does not seal anything. A rebate can also be seen in the pictures. Is there one there, or are the reveals flush without offsets? If a rebate is present, the windows would have had to be large enough so that they can be set against it from inside, and the compression tape would have belonged in between.

The rest of the window joint that is not filled by the compression tape is normally filled with PU foam. At temperatures below 5°C outside temperature, a winter foam must be used here because the normal foam otherwise does not expand properly and becomes crumbly. By the rest, I do not mean the width of the joint, but the rest of the depth. For example, with an 80mm frame width, 20mm are first fully filled and sealed from outside with the compression tape between frame and masonry. The remaining 60mm in depth are filled with suitable PU foam.

What is completely missing in your case is the inner sealing of the window joint! According to RAL, this must be executed inside as airtight and vapor-resistant or vapor-tight. This is professionally done with a window sealing tape (print: INSIDE or similar, usually pink) glued to the frame on the joint side BEFORE foaming, which should not be confused with the compression tape intended for the outer sealing. This is glued all around the frame, including the side that will later form the joint edge. This tape is between 7.5 and 15 cm wide and mostly protrudes inward. This window sealing tape is then glued inside to the reveal, either self-adhesive or if no adhesive strip is present with the appropriate adhesive, and is plastered over there. According to RAL, allowed as an alternative to this method (in addition to compression tape and PU foam in the window joint) is also the use of permanently elastic adhesive sealants with high vapor resistance on the inside of the window. The finish can therefore, if compression tape and PU foam were used properly, also be done with suitable acrylic spray sealants and the joint covered with a batten. This is often used in renovations so that no or less new plastering is necessary.

These are the RAL specifications, which do not necessarily have to be followed exactly, but the principle and concept should always be adopted:

Outer sealing: wind-driven rainproof, vapor-permeable, airtight
Filling of the window joint: PU foam high insulation, gap-filling
Inner sealing: airtight, vapor-tight or at least more vapor-tight than outside.

The lower window joint cannot always be formed RAL-compliant with existing window sills, but the principle should be maintained here: seal the joint between sill and window inside with acrylic, seal rainproof on the outside with an additional batten on the lower window edge connecting to the old sill, and fill the space as best as possible. Since you are renewing the interior window sills, nothing speaks against proper sealing here as on the sides either. Only the compression tape outside might be tight if the old sills remain. This, however, is not critical if the connection of the old sills to the new window is made watertight with a batten and a corresponding outer sealing tape.

In your case: Not windproof, since partly only PU foam is used, not rainproof, and also vapor-permeable from the inside, so condensation in the intermediate space is inevitable.

If you search for "window installation RAL" or similar, you will also find illustrations of the three layers (outer sealing, insulation layer, inner sealing). If you compare those with your situation, you will clearly recognize the mess.

For cleaning: It is important that the frame is dust-free and the compression tape adheres well; the reveal is not so critical, just no coarse dirt should be on it. Inside, normally an inner sealing tape is plastered anyway. This must be primed beforehand or the dust bound with some moisture, for example. Otherwise, since the plaster does not adhere anyway, there is no other option.
 

AltbauSan18

2018-03-05 18:36:12
  • #4
Wow, now that’s what I call a detailed answer. Thank you very much for that.
In the meantime, the compressible tape has indeed expanded, and it at least looks like everything is now covered. At least some degree of tightness should now be present. However, you said that the compressible tape must adhere well to the window frame. This is certainly not the case in some places. I cannot judge whether the pressure of the tape against the frame is sufficient for tightness. I assume not necessarily good or maybe not at all.
The depth is certainly not fully filled in all places.

Regarding your question "Is there one or are the reveals continuous without offset?"
Yes, the windows have an offset and the windows have been installed up to that point. However, there is no tape between the front of the window and the wall projection there.

So today the window installers came back and sealed from the inside. However, I haven't seen the result yet.

Unfortunately, nothing more will be done to make it rain- and windproof without scraping and removing. No idea whether something was repaired again.

Do you see a chance that they could still fix the mentioned errors? The foam or tape was certainly not removed and renewed.

Here are a few photos of the condition this morning:

For me, this matter is also about whether the labor costs for fine plastering and the costs for the compressible tape were even reasonable with this execution.

My walls are not plastered yet and I still have the chance to have everything corrected. But if the diffusion-tight tape is already on it, you obviously cannot see anymore whether they actually corrected something.

I will send more photos later to show the last work step.

Oh, and regarding the exterior window sills. Previously, there were concrete window sills installed that went through from inside to outside. The window installer insisted that these be removed because of the thermal bridge. I think that was really necessary.
 

dertill

2018-03-06 07:43:59
  • #5


If the compressible tape only rests on the frame on one side and on the foam on the other, it is still not tight. Only if the tape rests fully and continuously on both the frame and the masonry all around!



It must rest everywhere. If there are any voids between the tape and the frame, it’s useless. Adherence is helpful because the frame expands/contracts with temperature changes and otherwise the tape can be pushed out of the joint over time.



The compressible tape should have been installed exactly here. Except if the overlap is so small that even with perfectly fitting windows, less than 1 cm of support surface is available. That would then be too small to apply the tape. But that can no longer be done without removing the windows.



Just quickly hide the botch so nobody sees it! How were the inner window sealing tapes applied? From the inside onto the frame? Or was the side not fully foamed yet?



IF the inner sealing tape was applied correctly and thereafter the rest of the window joint was fully foamed without voids, this can still work without removing the windows. What you are still missing then is only the outer sealing layer. Do you plan to add an ETICS from outside? Then plaster profiles for the reinforcing plaster must be used on the window frame anyway, which are also rainproof and diffusion-open. Without ETICS, there are rainproof renovation sealing profiles (e.g. Reno Rechtsanwältin) which are glued from outside to the frame and seal the outer edge joint (according to the manufacturer) rainproof. Whether this also seals tight with the inner abutment of the window to the overlap, I don’t know. For that, the windows must definitely rest fully from the outside. Anyway, this is only the second-best solution. The correct installation of the compressible tape would have been much easier, cheaper, and less conspicuous. The window installer cannot excuse himself with too big window joints or cold temperatures. If he measured the windows and they don’t fit, it’s his own fault.
If the installation according to RAL was included in the offer, you can point out the incorrectly installed compressible tapes and complain that they are ineffective like this. If he causes problems, have him name the manufacturer and model and you can check the technical data sheet where there are certainly instructions for correct installation that were not followed here.



As presented, you could have saved the labor costs for the entire window installation and done it yourself. Just use Google once and anyone with common sense would place sealing tape in the correct place. Some plastering must be done with every window replacement; that can never be completely avoided. With correct interior sealing, the inner reveal must always be replastered. Without it only works if acrylic and cover strips are used, which works but the long-term durability is questionable.



Yes, that was the right decision.

The absolute minimum the window installer must do here is to completely fill the window joint with PU foam. The sealing tape inside does not bother because it also insulates but only, as installed, does not seal. Furthermore, the inner airtight and diffusion-tight connection as well as the outer airtight and rainproof connection.

If you have not prepaid too much, e.g. only 50% of the material price: Insist on scraping out, removing, and resealing the joint. Unless he can show you a technical data sheet or RAL guidelines based on your pictures that approve this procedure as permissible.

Edit: Photos were not uploaded with your post.

Good luck.
 

AltbauSan18

2018-03-07 19:50:51
  • #6
So, in the meantime I have also spoken with Würth service. The used compressible tape 66/5 - 10 is, as the name suggests, approved for joint widths up to 10 mm. Of course, it expands further (in my case up to 35 mm), but then none of the required RAL values are guaranteed anymore. The gentleman on the phone had of course never heard about the PU foam, and with this combination there will certainly never be any test results.

I think the foam will be wide enough in the joint in some places so that the tape adheres there with the specified expansion. That doesn’t help me at all, because as you already wrote, in this case it would at least have to be fully filled.

What particularly annoys me is that I already complained about this when installing the second window, but the window installer told me that the tape would then be pressed firmly enough and everything would be okay. But I didn’t believe that. That evening I read the specification of the tape and it was clear to me anyway. That I understood the specification correctly was also confirmed today on the phone. It’s not particularly complicated...

He could have simply used a different tape for 30 mm width at that time or had the plasterers apply 2 cm more, for all I care. Probably that day was simply scheduled for our house and could not be rearranged otherwise...
Then it just gets botched.

Wrong window contacts were delivered and they will be replaced. After that the sides will be sealed.

He also said that plaster profiles will be installed. But I don’t know if only inside or also outside.

Unfortunately, I’m very stressed at work right now, so communication with the window installer is out of the question to finally clarify everything.

The more it continues now, the more complicated the correction will be.

He claims everything is so good. I will probably not get around an expert report...

Nothing about RAL installation is stated on the offer. However, he mentioned it several times. And according to statements from the internet, you always have a claim to RAL installation unless you sign that you expressly agree to it being installed differently.

If a non-standard-compliant installation was not expressly agreed upon, you are entitled to window installation according to RAL.

So the law should be on my side. Warranty is also the only reason I didn’t install it myself. But I really don’t need a legal dispute. I hope he fixes it without making a fuss.

We will not insulate the house.

So now the promised pictures + some more of the sealing.


[ATTACH alt="fensterlaibung-dichtungsband-Fensterrahmen-fensterfuge-249098-1.jpg" type="full"]19435[/ATTACH]

Interior sealing
[ATTACH alt="fensterlaibung-dichtungsband-Fensterrahmen-fensterfuge-249098-2.jpg" type="full"]19436[/ATTACH]
[ATTACH alt="fensterlaibung-dichtungsband-Fensterrahmen-fensterfuge-249098-9.jpg" type="full"]19443[/ATTACH]
Exterior sealing
[ATTACH alt="fensterlaibung-dichtungsband-Fensterrahmen-fensterfuge-249098-8.jpg" type="full"]19442[/ATTACH]
Here also outside on the side of the window.
[ATTACH alt="fensterlaibung-dichtungsband-Fensterrahmen-fensterfuge-249098-7.jpg" type="full"]19441[/ATTACH]

At the roller shutter box
[ATTACH alt="fensterlaibung-dichtungsband-Fensterrahmen-fensterfuge-249098-6.jpg" type="full"]19440[/ATTACH] [ATTACH alt="fensterlaibung-dichtungsband-Fensterrahmen-fensterfuge-249098-4.jpg" type="full"]19438[/ATTACH]

 

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